OP asks the real life equivalent of being AFK which, assuming you’re normally regularly online, only really corresponds to being high or sleeping.
The funny thing is, it didn't occur to me how vague my question was until after I posted and started seeing the replies. That's made it more fun tbh, and interesting as in this context (online vs. in real life) I've not really thought of being online in such individualistic terms as this and some other replies suggest.